Interferons are currently classified into three groups: type I, type II and type III IFNs. The type I IFNs include all IFNαs, IFNβ, IFNε, IFNκ, IFNω and IFNν. Humans have 12 different IFNαs and a single IFNβ. The structure of interferon alpha is monomeric, composed of one chain, and two different receptor chains bind to different portions of the protein. This is different from interferon-gamma, which is a dimeric protein, and composed of two identical chains. The interferon alfa proteins are produced by leukocytes. They are mainly involved in innate immune response against viral infection. They come in 13 subtypes that are called IFNA1, IFNA2, IFNA4, IFNA5, IFNA6, IFNA7, IFNA8, IFNA10, IFNA13, IFNA14, IFNA16, IFNA17, IFNA21. Interferon alfa is also made as drugs for interferon therapy. They are pegylated interferon-alfa-2a, and pegylated interferon-alfa-2b.
The solution structure of recombinant human interferon alpha-2a (Roferon-A) has been determined by multidimensional heteronuclear NMR spectroscopy. The calculations using simulated annealing produced a family of 24 convergent structures which satisfy the experimental restraints comprising 1541 NOE-derived inter-proton distances, 187 dihedral restraints, 66 pairs of hydrogen bond restraints, and six upper and lower limits for two disulfide bridges. The fractional labeling of methyl groups allowed their direct and unambiguous stereospecific assignment which proved to be essential for obtaining a high resolution of the structures (Fig. 1).
Interferon-alpha-2b (IFNalpha2b) is the only effective adjuvant therapy for melanoma patients at high risk of recurrence that has been approved by regulatory authorities worldwide. However, IFN toxicities increase the risk of poor treatment compliance and impair the potential for benefit from this agent. PEG Intron (pegylated interferon-alpha-2b [IFN-alpha-2b]; Schering-Plough, Kenilworth, NJ) has demonstrated delayed clearance and increased area under the curve compared with native IFN-alpha-2b. Studies in patients with chronic hepatitis C infection and malignancies have demonstrated both biologic and clinical activity of PEG Intron and have provided empiric data to compare the pharmacokinetics (PK) and pharmacodynamics of PEG Intron and IFN-alpha-2b.